The present invention relates to a CCD image pickup apparatus.
A monochrome area CCD having a high density of picture elements has a plurality of separate video signal output lines. As shown in FIG. 8, this type CCD is a CCD 100 having plural horizontal scanning lines designed in such a way that a plurality of picture elements are arranged along each of the horizontal scanning lines in the form of identification numbers "1 2 3 . . . n, 1 2 3 . . . n, . . . n". Video output signals are produced along each of the horizontal scanning lines in the form of identification numbers "1 2 3 . . . n, 1 2 3 . . . n, . . . n" from the CCD 100. The picture elements are in parallel with the video output signals along the horizontal scanning lines.
It is an advantageous effect of such a type CCD that the frequency of one picture element is only l/n of that of the prior art image pickup apparatus during the video signal processing and actuation of the CCD.
FIG. 9 schematically shows an apparatus for projecting on a monitoring TV or the like the video output signals which are picked up by and produced from the CCD 100. The video output signals numbered "1 2 3 . . . n" are introduced into a synthesizing means 14 by way of plural CCD video signal lines having the numbers "1 2 . . . n" from the CCD 100. The plural video signals having the numbers "1 2 . . . n" from the CCD 100 are synthesized so as to produce a single video signal 15.
The video signal 15 is amplified by a video signal amplifier 16. This amplified signal is introduced into a video signal forming means 17 where various treatments such as addition of pedestal levels and/or synchronizing signals, gamma amendment and so on are carried out so as to produce a video signal output 18, in order to project the video signals on the monitoring TV or the like.
FIG. 10 shows an example of the synthesizing means 14 in which n is 3. For example, the synthesizing means 14 includes a sampling-hold means 10 for sampling-holding three video output signals d, e, f from the CCD and an analog switch portion 11 for synthesizing three output signals g, h, i after the sampling holding operation. If these video output signals d, e, f are already sampling-held, the sampling-hold means 10 is not necessary.
FIG. 11 shows one picture element arrangement in the CCD 100 having plural horizontal scanning lines The picture elements numbered "1 2 3 1 2 3 . . . 1 2 3" are arranged along each horizontal scanning line. The numbers "1 2 3" are arranged in a single picture element. If all picture elements along each horizontal scanning line are processed in order to produce desired electric signals, as shown in FIG. 12, it takes about 63.5 micro seconds. Therefore, signals from a single picture element can be obtained for the period which is about the scanning time per one horizontal scanning line (=63.5 micro seconds)/the number of the picture elements in a single horizontal scanning line.
Assuming that the video output signals d, e, f from the CCD 100 are not sampling-held, the operation of the sampling-hold means 10 and the analog switching portion 11 will be explained, referring to FIG. 13.
As the video output signals A of the CCD 100 are the signals d, e, f in the form of analog signals, these signals d, e, f are sampling-held in response to the signals a, b, c (FIG. 10) of the sampling-hold pulses B. After the sampling-hold operation, the output signals C become the signals g, h, i as shown in FIG. 13. Incidentally, the output timing of the sampling-hold pulses is not limited to this mode and can be changed depending on a structure and use of the CCD.
The sampling-held output signals g, h, i are to be synthesized by the analog switching portion 11 shown in FIG. 10. The analog synthesized pulse signals D such as the signals j, k, l in FIG. 13 are introduced into the analog switching portion 11 which is switched to be open only in a high condition. As a result, a synthesized video signal like the signal m in FIG. 13 can be obtained in an ideal condition. In practice, however, the synthesized video signal n having noises is produced in the shape of a wave because they are affected by the digital waves such as the sampling-hold pulses a, b, c and the synthesized pulse signals j, k, l. The above-stated explanation can be also applied to plural lines having any number n.
In the prior art, plural CCD video output signals having the number n are synthesized into a single CCD video output signal. As shown in FIGS. 13 and 14, spike noises SP produced at interconnection portions of adjacent picture elements and ringing and overshoot produced by synthesizing thereof affect the signals as noises N (hereinafter called synthetic spike noises). If the gain is set high so as to increase the sensitivity, those synthetic spike noises are emphasized so that longitudinal stripes or fringes can be observed on the monitoring TV. In addition, the resolution is decreased to a remarkable degree. As a result, it is very difficult to obtain a clear picture image having high resolution and high density.
In order to solve such a problem, it can be proposed to introduce the synthesized output into a filter so as to remove or cancel the synthetic spike noises. However, if such a filter is provided for the purpose of removing the synthetic spike noises, the resolution is decreased.
As shown in FIG. 15, it can be proposed to provide an amplifier Amp in each of the plural video output signal lines connected to the CCD 100 so as to amplify the signals and thereafter synthesize the signals in a synthesizing means 14. If plural amplifiers Amp are provided, however, arrangement space, consumed power, noises and so on must increase. Therefore, such a proposal is not practical.